Manufactured fibers and nonwoven textiles including such fibers have many different uses in commercial and consumer products. For example, manufactured fibers are often used in absorbent articles such as diapers, feminine hygiene articles, wipes, clothing, packaging, towels, tissue, surgical wraps and gowns, wall coverings, automotive, aeronautic, military and nautical applications, as well as building materials, writing media, filters and insulation. Due to the demand for manufactured fibers of different types having different characteristics, a number of fiber forming methods and apparatuses have been developed.
Some of the most popular fiber forming techniques include melt-blowing, wet spinning and dry spinning. In each of these methods, the fiber material is softened into a flowable state and forced through a die and/or spinnerette to form embryonic fibers that are then typically mechanically stretched to form the desired end fibers. Melt-blowing of fibers generally includes melting a thermoplastic material, forming a fiber and then cooling the thermoplastic material to form solid fibers. Wet spinning generally involves extruding fibers formed from a solution of polymer and solvent into a coagulating bath, such as a solution of sodium sulfate in water. Dry spinning typically involves extruding a solution of polymer and solvent into air to form solid fibers. The fibers formed by these methods are often collected on a surface such as a belt to form a nonwoven web or are otherwise treated chemically or mechanically manipulated to change or enhance their properties. Examples of methods and apparatuses for melt-blowing and spinning fibers are described in U.S. Pat. No. 3,825,379 issued to Lohkamp; U.S. Pat. Nos. 4,826,415 and 5,017,112 issued to Mende; U.S. Pat. No. 5,445,785 issued to Rhim; U.S. Pat. Nos. 4,380,570; 5,476,616 and 6,013,223 issued to Schwarz and U.S. Pat. No. 6,364,647 B1 issued to Sanborn.
However, despite the success of such known methods and apparatuses, there is a need in the art for improvement. For example, it would be desirable to provide a method and apparatus for more efficiently forming fibers. It would also be desirable to provide a method and apparatus for forming smaller and/or more uniformly sized fibers. Further, it would be desirable to provide a method and apparatus for forming fibers, wherein the pressure drop associated with the attenuation medium in the die is relatively small as compared to known fiber making apparatuses and methods. It would also be desirable to provide a method and apparatus of forming fibers wherein a reduction in the pressure difference between the attenuation medium inside the apparatus and after it exits the apparatus allows for higher relative solvent-vapor content levels in the attenuation medium in the attenuation region as compared to existing fiber forming methods and equipment. Even further, it would be desirable to provide a method and apparatus for forming fibers from non-thermoplastic and/or solvent-soluble materials. Further yet, it would be desirable to provide a high throughput die apparatus including multiple rows of spinning orifices that can form fibers from non-thermoplastic and/or solvent-soluble materials. Still further, it would be desirable to provide a method and apparatus for forming fibers wherein a low pressure drop associated with the attenuation medium in the die provides for high relative solvent-vapor content levels even when the flow rate and/or velocity of the attenuation medium is similar to conventional dies.